A beam of red light has twice the intensity as a second bean of the same color

[looi76]

Homework Statement

A beam of red light has twice the intensity as a second bean of the same color. Calculate the ratio of the amplitude of wave.

Homework Equations

$$intensity \propto (amplitude)^2$$

The Attempt at a Solution

$$1^{st} \mbox{ beam} = 2I$$
$$2^{nd} \mbox{ beam} = I$$

I don't know if this step is correct and I don't know what to do next?!

 

[Antenna Guy]

Homework Equations

$$intensity \propto (amplitude)^2$$

The Attempt at a Solution

$$1^{st} \mbox{ beam} = 2I$$
$$2^{nd} \mbox{ beam} = I$$

$$I_1=2 I_2$$

$$\frac{I_1}{I_2}=2$$

What can you do to the above relation (given your relevant equation) to convert it to a ratio of amplitudes?

Regards,

Bill

 

[looi76]

$$intensity \propto (amplitude)^2$$

So, it will be $$1:4$$ ?

 

[Defennder]

No, start off by expressing both intensities I = kA^2. Then compare the ratio of each amplitude to the other.

 

[Antenna Guy]

$$intensity \propto (amplitude)^2$$

So, it will be $$1:4$$ ?

No. Try what Defennder suggested to see why.

Regards,

Bill